How to wipe my pc .from scratch?

i wantt to know how do i wipe my pc cos my computer is taking so long to load pages and and i need to wip it clean and start again my pc is advent and it has windows 7 in in . the only disks i got with my pc are micrisift works se9 and thats it and when i go to recovery options it wont let me do it cos it says u need to do a back up and put it on a blank cd which i dont have either .